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Topic: Bearings for a wooden clock? (Read 34443 times)

Bearings for a wooden clock? I've probably used them all...Each bearing technique mentioned in the posts so far has it's merits and limitations. I've finally realized that each clock design and even each arbor location is different, and deserves it's own solution.My experiences and rambling comments on each:

Wood on Wood: My first clock was a "totally wood" clock (I soon got over that...) with oak shafts in birch ply frame pivots. It's worked flawlessly for years. The arbors were burnished (in a drill press) with another piece of birch. The pivots were burnished with a dowel in a drill. They were then "treated" with a little graphite. The graphite does blacken the wood and can leave messy stains. When I use wood on wood now, I use "dry white lube" (teflon powder). Wood on Wood is by far the easiest and cheapest solution. It works fine on intermediate arbors, and I still use it when I can, but not on Great wheel arbors or escape shafts. (more on that later...)

Lignum Vitae: 'Tried it, don't like it. If used with a metal shaft (brass or steel), it creates the sticky residue Marc spoke of in his post. It works best with oak (hard and porous) arbors. But it's no better than graphite or white lube, and therefore isn't worth the effort to me. Lignum Vitae DOES however make the most excellent pallets!

Teflon: Teflon (PTFE) tubing is readily available and inexpensive. Slicing the appropriate size tube into bearing inserts is easy and works great... in SOME applications. There are two properties of pure teflon that dictate when/where it makes sense to use. While it has a low dynamic coefficient of friction (it's very slippery), it has an extremely low STATIC coefficient of friction. Most materials take more force to START motion than to MAINTAIN it ("static" vs. "dynamic"). This property makes teflon an excellent bearing material for start/stop applications - specifically, escape wheels. The other important application property of teflon is called "creep" (not a character judgement!). While it is "strong", it's not very "hard", but the worst is: under load it "flows". Under high load, teflon almost behaves like a liquid - a very THICK liquid, but liquid just the same. If used for a Great wheel arbor for instance, at first it would appear to work great. But over time (months), it will actually flow and the arbor will no longer be in the center of the bearing! Enough force and enough time, and the arbor will end up on the edge of the bearing - not good. The bottom line: teflon makes great escape shaft bearings, and even third or fourth wheel bearings. It also makes the best pivots for grasshopper arms and gravity escape arms. But NOT Great wheel, main wheel or 2nd wheel.

Nylon: Nylon, delrin and other "plastic" bearings are inexpensive and easy. They work well with wood or metal shafts. They're not as slippery as teflon, but don't have the "creep" problem. They do however exhibit a similar phenomena: as the load increases, the coeficient of friction increases. Still, they work well in most applications.

Ball Bearings: I was reluctant the first time I used ball bearings - after all, this is a WOODEN clock! There's no point explaining their advantages - these are real. But the disadvantages: A shielded bearing has almost as much friction as some of these other designs, but an unshielded bearing is very unforgiving for dirt, sawdust, and all the other things that go with a wooden clock. They're relatively expensive. They require very tight tolerances. That said, they do have some good applications. They make sense in places where very low friction is most important - like escape shafts, 4th wheels. Because they're ultimately strong, they also shine in high-load applications like Great & main wheels. But they're a waste on intermediate shafts. And never use them for back-and-forth applications - like pendulum support or escape arms.

Brass Bushings: (And other metal-on-metal bearings) The first rule: never use the same material for the shaft and for the bearing. In other words, don't use a brass shaft in a brass bushing. Without going technical, dissimilar metals will always have a better coeficient of friction than the same material on itself. Brass, aluminum, and steel tubing and rod are readily available, inexpensive, and easy to make bearings and shafts from. I've used probably every combination of all, and sometimes even with wooden arbors. My favorite is steel shaft in brass. In my opinion, metal bushings are the best combination of low friction, cost and ease-of-build. One more comment: they have lower friction if oiled, but avoid it if you can - it attracts dust, leaves a mess, and will eventually foul the works.

One more very good combination (that didn't fit into one of these clasifications) is a brass shaft in an un-bushed wood (birch ply) pivot hole. This is the easiest, cheapest "bearing".

I've tried other bearing schemes and materials, but these are the basics.As final note: one of my more recent clocks - a spring-powered gravity-escape table regulator - used EVERY ONE of these bearings, in all the right places. It is the most efficient, most reliable, and most accurate clock I've built!

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- rabbit

Damon Miller

Rabbit that was an excellent critique of bearing materials used in wooden gear clocks. I have found similar results in my wooden clock designing/building, but never took the time to put my findings into words. Thanks for your time and expertise.

Rabbit- I seen your postings on other sites and as on them, you share excellant info. What can you tell a novice about the pros and cons of the traditional bone bearings.? Does anyone know a commercial source for good bone? Will tagua nut work in place of bone? Thank you, Reid PS I am so please to find this long over due forum. Thank you, Mr. Beall or whoever was nice enough to start this. I am really looking forward to the postings.

Reid-I've not used bone bearings, but you have my curiousity up.I know a lot of the old traditional clocks used tallow (animal fat) as a lube, and bone may have similar properties - sort of like lignum vitae, self-lubricating?I welcome any other comments from someone who's used it.

Addition to roller bearings.I have had some success with sealed roller bearings. Thereare 2 types. nylon seal and metal seal. The nylon in the nylon seal ones actually touch the race, so are no good. The metal sealed ones are hard to clean the grease out of, exept if you you use a hydrocarbon brake cleaner. Also... use bearings that have more 'play' in them, as the don't 'lock up' then the clock frame is twisted. You can order bearings which have certain amounts of play built into them...like high speed baerings have more play in them for when they heat up and expland.cheersrosco

p.s. also bearings can be problematical on the escapement wheel, where the smallest amount of grit can halt the wheel turning

My design used 3/16" steel shafts with brass bushings. The fit was nice and loose when uninstalled but very unforgiving of imperfections in frame alignment. I recently bought a kit with precut pieces to see if I could learn something (and so I could actually have something to hang on my wall). Although the kit used wood arbors with plastic shoulder bushings, there was a large amount of play (about 0.020") between the arbor and bushing. I usually use Mcmaster Carr to buy my hardware, but I can't seem to find anything that would fit 3/16" shafts with that sort of clearance.

The long and short is this: What type of bearing/shaft fit have you experimenters found to be most suitable?

I have never used bearings or brass bushings in any of my wooden gear clocks. I always use brass arbors. I typically drill a hole in the clock frame that is 1/64 of an inch larger than the actual arbor diameter. I always end up with a clock that works and has very little maintenance. You can see my clocks at Www.ontimewoodenclocks.com

A very good piece on bearings that should save many people a lot of time and frustration. My experience has been much the same. I recently found, however, that the lignum vitae currently available is not the same as the old stuff that Harrison used. I can't recall where I read this but unless you can get some old bowling balls, the wood will be oily and leave that sticky residue.

I am unable to easily source lignum where I live so "necessity being the mother of invention" has lead me to some other tricks. I sometimes I push some soft (just melted) paraffin into the arbor holes using a piece of polished brass rod dipped in wax. I use the polished brass rod to burnish the wax into the sides of the arbor hole. Burnishing leaves a thin film and the wax will not clog the hole. The loose wax is then blown out. I always try to get by without using it but is one of those techniques in my arsenal of tricks to get a clock running. I find that there is a significant difference to how well the wheels turn before and after application of wax. I usually do this during my final assembly.

This summer I visited George Bruno of Torrington CT who is an acknowledged expert on early American wooden works clocks. He has worked on many wooden works clocks that have been running for almost 200 years. I discussed with him the use of bone for bearings as was very common in the early 1800s and even before. My interest in this is I make reproduction wooden works of this time frame and have had a hard time finding the right bone. George said he had been experimenting and he and his son Donald who sole occupation is the repair and restoration of wooden wheel clocks had had very good results with using bamboo flooring for the bearings. It is the type that is currently sold as a laminate flooring. George showed me the bearings that he had made from the bamboo flooring and that seemed to be very satisfactory. George does not have a computer so contact with this fantastic clock guru is limited to phone or letter or personal contact which is very freely given. His son Donald has a web site which I believe is Torrington clock co. Reid Heilig

I've made three clocks so far, all with ply front and rear plates and brass arbors directly in holes drilled in the ply. They seem to work perfectly at first, but after a time they accumulate some dark stuff which creates the dreaded friction. Not difficult to clean out with gentle filing, but where does it come from? I guess it is from the adhesive in the ply wood. Anyone had this problem?I've tried using silicon as a lubricant (applied by spraying onto a piece of dowel that fits loosely into the bearing.) It seems to work, but I don't know what will happen in time - will it dry out? or will it attract dust? or just dry out and become sticky?My plan B will be to apply cyano adhesive to the bearing, which penetrates and hardens and seals the surface, followed by a light filing to remove any surface layer. I've used this technique on threads cut in wood with good success. Anyone got any thoughts? Rabbit?